I can understand the fact that your boss likes you to dress appropriately. But really if you aren't being vulgar with your tie I don't see a problem showing off the team you like!  Obviously my opinion is different than this person

From Chicago's WGNtv.com comes the unfortunately real story of a Chicago car salesman who was fired because he wore a Green Bay Packers tie to work

(via Chicago man wears Packers tie to work, is promptly fired - Shutdown Corner - NFL  - Yahoo! Sports.)